U.S. patent number 8,157,532 [Application Number 12/154,570] was granted by the patent office on 2012-04-17 for wind turbine blade with anti-noise devices.
This patent grant is currently assigned to Gamesa Innovation & Technology, S.L.. Invention is credited to Luis Miguel Garcillan Rueda, Alvaro Matesanz Gil.
United States Patent |
8,157,532 |
Matesanz Gil , et
al. |
April 17, 2012 |
Wind turbine blade with anti-noise devices
Abstract
A wind turbine comprising at least a blade (11) having an
aerodynamic profile with a leading edge (13), a trailing edge (15)
and suction and pressure sides between the leading edge (13) and
the trailing edge (15) that includes an anti-noise device (31)
placed on the suction side formed by elements (33) that modify the
frequency spectra of the boundary layer noise. Preferably the
anti-noise device (31) is placed on the suction side between two
sections corresponding to chord positions in the range of 40%-95%
of the chord length, measured from the leading edge (13).
Inventors: |
Matesanz Gil; Alvaro (Madrid,
ES), Garcillan Rueda; Luis Miguel (Madrid,
ES) |
Assignee: |
Gamesa Innovation & Technology,
S.L. (Sarriguren, ES)
|
Family
ID: |
40088438 |
Appl.
No.: |
12/154,570 |
Filed: |
May 23, 2008 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20080298967 A1 |
Dec 4, 2008 |
|
Foreign Application Priority Data
|
|
|
|
|
May 31, 2007 [ES] |
|
|
200701494 |
|
Current U.S.
Class: |
416/235;
416/236R; 415/914 |
Current CPC
Class: |
F03D
1/0608 (20130101); F05B 2240/30 (20130101); Y02E
10/72 (20130101); F05B 2250/183 (20130101); F05B
2260/962 (20130101); F05D 2240/127 (20130101); F05D
2250/183 (20130101); F05B 2240/3062 (20200801); F05B
2240/122 (20130101); Y10S 415/914 (20130101); F05D
2270/17 (20130101); F05D 2240/30 (20130101); F05D
2260/962 (20130101) |
Current International
Class: |
F03D
1/06 (20060101) |
Field of
Search: |
;415/914
;416/235,236R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
WO2006/122547 |
|
Nov 2006 |
|
WO |
|
Primary Examiner: Look; Edward
Assistant Examiner: McDowell; Liam
Attorney, Agent or Firm: Ladas & Parry LLP
Claims
The invention claimed is:
1. A wind turbine comprising at least a blade (11) having an
aerodynamic profile with a leading edge (13), a trailing edge (15)
and a suction side and a pressure side between the leading edge
(13) and the trailing edge (15), wherein the blade (11) includes an
anti-noise device (31) placed on the suction side formed by a
plurality of elements (33) which are bodies of an arrow shape, said
bodies being defined by left and right upper and lower trapezoidal
faces (51, 53, 55, 57) with common central sides from an arrow tip
(41) to an arrow center (43) and lateral faces (61, 63, 65, 67, 69,
71) extending between said upper and lower trapezoidal faces (51,
53, 55, 57), that modify a frequency spectra of boundary layer
noise.
2. The wind turbine according to claim 1, wherein said anti-noise
device (31) is placed on the suction side between two sections
corresponding to chord positions in a range of 40%-95% of a chord
length, measured from the leading edge (13).
3. The wind turbine according to claim 2, wherein said anti-noise
device (31) is placed along a section of the blade (11) extending
between 5% to 100% of its length measured from its root (19).
4. The wind turbine according to claim 3, wherein said anti-noise
device (31) is placed along a section of the blade (11) extending
between 66% to 100% of its length measured from its root (19).
5. The wind turbine according to claim 1, wherein the plurality of
elements (33) of the anti-noise device (31) are placed on the blade
(11) individually, leaving spaces between them.
6. The wind turbine according to claim 1, wherein the elements (33)
of the anti-noise device (31) are placed on the blade (11) in
groups, leaving spaces between the groups.
7. The wind turbine according to claim 1, wherein the plurality of
elements (33) of the anti-noise device (31) are placed on the blade
(11) side by side without leaving spaces between the plurality of
elements (33).
8. The wind turbine blade according to claim 1, wherein said
elements (33) are placed on the blade (11) with the arrow tip (41)
oriented towards the leading edge (13).
9. The wind turbine blade according to claim 1, wherein said
elements (33) are placed on the blade (11) with the arrow tip (41)
oriented towards the trailing edge (15).
10. The wind turbine blade according to claim 1, wherein heights
(t1, t2, t3 and t4) of, respectively, the arrow tip (41), the arrow
center (43), and arrow left and right ends (45, 47) are comprised
between 0-10 mm.
11. The wind turbine blade according to claim 10, wherein the
height (t1) of the arrow tip (41) is less than the height (t2) of
the arrow center (43) and the heights (t3, t4) of the arrow left
and right ends (45, 47) are less than the height (t2) of the arrow
center (43) and greater than the height (t1) of the arrow tip
(41).
12. The wind turbine blade according to claim 1, wherein a first
angle (.theta..sub.1) between an outer side (75) of the left upper
face (51) and an arrow axis (77) is comprised between 5-60 degrees
and a second angle (.theta..sub.2),between the outer side (79) of
the right upper trapezoidal face (53) and the arrow axis (77) is
comprised between 5-60 degrees.
13. The wind turbine blade according to claim 1, wherein a third
angle (.theta..sub.3)between an inner side (81) of the left upper
trapezoidal face (51) and an arrow axis (77) is comprised between
30-90 degrees and a fourth angle (.theta..sub.4) between an inner
side (83) of the right upper trapezoidal face (53) and the arrow
axis (77) is comprised between 30-90 degrees.
14. The wind turbine blade according to claim 1, wherein a first
length (.lamda..sub.1) of a side (85) connecting inner and outer
sides (81, 75) of the left upper face (51) is comprised between
0-20 cm, a second length (.lamda..sub.2) of the side (87)
connecting inner and outer sides (83, 79) of the right upper
trapezoidal face (53) is comprised between 0-20 cm and a third
length (.lamda..sub.3) of a side projection of said elements (33)
is comprised between 0-20 cm and a fourth length (.lamda..sub.4) of
a frontal projection of said elements (33) is comprised between
0-20 cm.
Description
FIELD OF THE INVENTION
The invention relates to wind turbine blades with anti-noise
devices and in particular with devices intended for reducing the
aerodynamic audible noise produced in dB(A).
BACKGROUND
An important constrain in the power production in wind turbines is
that imposed by the noise generated during operation. In
particular, wind turbine blades produce aerodynamic audible noise
due to the interaction between the boundary layer and the trailing
edge.
Turbulent boundary layers on wind turbine blades produce noise
after the onset of the transition and when interacting with the
trailing edge. The anisotropy, history and length scale of the
turbulence within the boundary layer affect the noise generated by
an airfoil.
There are known several proposals for reducing the aerodynamic
noise produced by wind turbine blades.
One of them is the use of serrated trailing edges. In this respect,
EP0652367 discloses rotor blades having its rear edge irregularly
formed, in particular in a saw-tooth form. EP1314885 discloses
rotor blades with serrated trailing edges each having a plurality
of span-wise, periodic indentations, in the form a saw teeth having
approximately 60 degrees included angles between adjacent vertices.
EP1338793 discloses rotor blades in which a dentation is formed in
the trailing edge part of the blade which is shaped in a serration
of triangular tooth, of trapezoid tooth, or of sawtooth.
Another proposal, disclosed in WO2006/122547, is the use of
turbulence generating means as noise reduction means. Said means
are placed on the leeward surface side of the wind turbine blade
and at the outer section of the wind turbine blade in direction of
the blade tip.
The prior art also teaches the use of wind turbine operational
control methods for reducing the aerodynamic noise and, in
particular, controlling the rotor speed. In this respect, the
publication "Wind Turbine Noise", Wagner et al., Springer-Verlag
Berlin Heidelberg 1996 summarizes the problems raised by the noise
produced by wind turbines and some proposals for its reduction.
The present invention provides a different solution for reducing
the aerodynamic noise produced by the wind turbine blades.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a wind turbine
blade with means that allow altering the characteristics of the
boundary layer and therefore modify the emitted noise.
Another object of the present invention is to provide a wind
turbine blade with audible noise reduction means. Although the
acoustic energy in the noise emission may remain unaltered, the
audible noise production will be reduced.
These and other objects of the present invention are met by
providing a wind turbine comprising at least a blade having an
aerodynamic profile with a leading edge, a trailing edge and
suction and pressure sides between the leading edge and the
trailing edge and including an anti-noise device placed on the
suction side formed by elements that modify the frequency spectra
of the boundary layer noise.
As it will be explained in detail below, said elements are not
intended to produce turbulence as a mechanism for noise reduction
like in WO 2006/122547 but coherent fluidic structures. The
introduction of turbulence implies the introduction of random
motion in the boundary layer, while the introduction of coherent
structures is associated to the introduction of ordered motion in
the boundary layer.
Other features and advantages of the present invention will be
understood from the following detailed description in relation with
the enclosed drawings.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a schematic side view of a wind turbine blade with an
anti-noise device according to the present invention.
FIG. 2 is a perspective view of a single element of an anti-noise
device according to the present invention.
FIG. 3 is a plan view of the single element shown in FIG. 2.
FIGS. 4, 5 and 6 are perspective views of three different
embodiments of an anti-noise device according to the present
invention.
FIG. 7 shows schematically the coherent vortical structures
generated by a single element of an anti-noise device according to
the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
When the flow goes over a blade, a boundary layer is formed. This
boundary layer is the region in the flow field where the velocity
adapts from the velocity in the flow away from the blade and the
non-slip condition that is naturally imposed on the surface of it.
The nature of the boundary layer can be laminar or turbulent. A
laminar boundary layer could be seen as a boundary layer where the
flow moves smoothly, like in layers parallel to the surface.
Laminar boundary layers naturally develop into turbulent boundary
layers, where there is a high component of random motion. The
change from laminar to turbulent occurs in a region called
"transition region", where different fluidic structures develop
changing the nature of the boundary layer. The first turbulent
structure to appear is the "turbulent spot". Turbulent spots travel
downstream, merge and develop into .LAMBDA. structures (also called
hairpin structures). The latter structures promote mixing in the
boundary layer, and due to the motion patterns introduced in the
flow, they are self-maintained. Short after the appearance of the
.LAMBDA. structures the flow becomes completely turbulent, and no
instantaneous order can be found. In turbulent boundary layers
"real" viscous effects (those due to the viscosity) are only
present in the viscous sub-layer, which is a very small region
close to the wall. In the rest of the turbulent boundary layer the
viscous effects are only apparent, as they are due to the random
motion and not to the viscosity and shear stress energy
dissipation.
The power levels of noise emitted and its distribution in
frequencies highly depends on the length scale of the turbulence
and the power spectra of the pressure fluctuations introduced on
the surface of the blade by the turbulent motion. The scale of the
turbulent structures within the boundary layer is of the same order
of the boundary layer thickness, and its characteristic length
scales and power spectra distribution are highly dependent on the
history of the boundary layer upstream of the location considered,
which, for aeroacoustic purposes, is usually the trailing edge.
It is the idea of this invention to alter both, the scale of the
turbulence and its power distribution in the frequency domain by
the use of elements introducing coherent fluidic structures, placed
behind the location of the transition line, where the change from
laminar to turbulent boundary layer occurs.
FIG. 1 shows a wind turbine blade 11 having a leading edge 13 and a
trailing edge 15 that includes an anti-noise device 31 according to
this invention placed on the right side--from the point of view of
the wind direction 17--of the transition line 21 where the change
from a laminar boundary layer to a turbulent laminar layer
occurs.
When the flow near the blade goes over the anti-noise device,
coherent vortical structures 35 (see FIG. 7), aligned with the
free-stream are produced, dramatically altering the boundary layer
and changing its fluidic characteristics. Streamwise aligned
coherent vortices have shown to have a great impact on the velocity
distribution on the boundary layer and on its turbulent
characteristics, i.e. turbulence levels, turbulent kinetic energy
production, etc.
In modern wind turbine blades it can be considered that the
transition line 21 is located, for moderate angles of attack,
between two sections corresponding to chord positions in the range
of 40%-95% of the chord length, measured from the leading edge
13.
FIG. 1 shows the anti-noise device 31 extending from the root 19 to
the tip 22. It is thought that the anti-noise device 31 shall be
placed along a section of the blade 11 extending between 5% to the
100% of its length measured from its root 19.
In another embodiment the anti-noise device 31 is placed along a
section of the blade 11 extending between 66% to the 100% of its
length measured from its root 19.
FIG. 2 shows an embodiment of a single element 33 that can be used
in the anti-noise device 31 in its position with respect to the
flow direction indicated by the x-axis and the blade span indicated
by the z-axis.
Following FIGS. 2 and 3 it can be seen that the single element 33
is a body of an arrow shape which is positioned on the suction side
of the blade 11 with the arrow tip 41 oriented towards the leading
edge 13.
In another embodiment the single element 33 is positioned on the
suction side of the blade 11 with the arrow tip 41 oriented towards
the trailing edge 15.
The element 33 is defined by left and right upper and lower
trapezoidal faces 51, 53, 55, 57 with common central sides from the
arrow tip 41 to the arrow center 43 and lateral faces 61, 63, 65,
67, 69, 71 extending between said upper and lower faces 51, 53, 55,
57.
In a preferred embodiment the heights t1, t2, t3 and t4 of,
respectively, the arrow tip 41, the arrow center 43 and the arrow
left and right ends 45, 47 are comprised between 0-10 mm.
In another preferred embodiment the height t1 of the arrow tip 41
is less than the height t2 of the arrow center 43 and the heights
t3, t4 of the arrow left and right ends 45, 47 are less than the
height t2 of the arrow center 43 and greater than the height t1 of
the arrow tip 41.
In a preferred embodiment the angle .theta..sub.1 between the outer
side 75 of the left upper face 51 and the arrow axis 77 is
comprised between 5-60 deg, the angle .theta..sub.2 between the
outer side 79 of the right upper face 53 and the arrow axis 77 is
comprised between 5-60 deg, the angle .theta..sub.3 between the
inner side 81 of the left upper face 51 and the arrow axis 77 is
comprised between 30-90 deg and the angle .theta..sub.4 between the
inner side 83 of the right upper face 53 and the arrow axis 77 is
comprised between 30-90 deg.
In a preferred embodiment the length .lamda..sub.1 of the side 85
connecting the inner and outer sides 81, 75 of the left upper face
51 is comprised between 0-20 cm, the length .lamda..sub.2 of the
side 87 connecting the inner and outer sides 83, 79 of the right
upper face 53 is comprised between 0-20 cm, the length
.lamda..sub.3 of a side projection of element 33 is comprised
between 0-20 cm and the length .lamda..sub.4 of a frontal
projection of element 33 is comprised between 0-20 cm.
FIG. 4 shows an anti-noise device 31 formed by a plurality of
elements 33 placed on the blade individually, without leaving
spaces between them.
FIG. 5 shows an anti-noise device 31 formed by a plurality of
elements 33 placed on the blade in groups, leaving spaces between
the groups.
FIG. 6 shows an anti-noise device 31 formed by a plurality of
elements 33 placed on the blade side by side leaving spaces between
them.
Varying the geometrical dimensions already defined and the spacing
between elements 33, different vortical strengths and core sizes
can be obtained for the coherent vortical structures. Geometrical
dimensions of the elements 33 have an impact on the fluidic
characteristics of the generated filaments, and therefore can be
tuned to be used over a wide range of wind turbine operating
characteristics for noise reduction purposes. In all the cases the
change in the velocity and vorticity distributions within the
boundary layer is expected to shift the noise power spectra
distribution (in dB(A)).
Although the present invention has been fully described in
connection with preferred embodiments, it is evident that
modifications may be introduced within the scope thereof, not
considering this as limited by these embodiments, but by the
contents of the following claims.
* * * * *